This invention relates generally to processes for recovering hydrocarbon product from bitumen or oil laden sands. More specifically, the present invention relates to the process for separating bitumen and related product from tar sands.
Tar sand deposits are known to occur in many of the same areas as petroleum deposits. The largest known reserves of tar sands are found in Canada, in the Northern Alberta deposit called the "Athabasca tar sands". Other large reserves are located in Venezuela, Utah, Oklahoma, Europe and Africa. It has been estimated that approximately sixty-five percent (65%) of all known oil in the world is contained in tar sand deposits, but owing to the difficulties in extracting the oil, little exploitation of the tar sands has taken place notwithstanding a significant world wide demand for crude oil products.
The makeup of the tar sands varies by region, with the Athabasca tar sands being the richest at approximately twelve to thirteen percent (12%-13%) bitumen content by weight. The tar sands in Oklahoma have been reported to contain approximately eleven percent (11%) oil by weight, while the Utah tar sands have been classified at five to thirteen percent (5%-13%) by weight oil content. The richness of the various tar sands can be evidenced by their dark brown to black color. The physically apparent properties of tar sands have caused them to be utilized as paving materials and as "pitch" in earlier times. The present day economics, however, dictate increased importance of the tar sand reserves as a viable alternative to the usual crude oil resources upon which the petroleum related industries rely.
Previous attempts have been made to commercially exploit the tar sands. Those related to the extraction of oils or bitumens have generally failed to prove out economically. As will be seen, these failures are predictable given the chemical circumstances of the prior art where significant energy or chemical inputs are needed to achieve practicable yields of oil or bitumen product.
The bulk of commercial processing of tar sands has resulted from the mining of the Athabasca deposits. The fundamental process utilized for these deposits relies on preconditioning with steam, hot water and alkaline (sodium hydroxide) adjustments to the pH. The vessel is typically rotated or the tar sands agitated in order to reduce the particle sizes. Following this preconditioning, the resulting pulp is transferred and retained in gravity settlers. The initial recovery of bitumen occurs as recovered product floating to the top of the settling vessel. Further processing for secondary recovery of bitumen by means of floatation cells occurs with collection of bitumen in the froth.
The recovered amounts of bitumen in the above described Athabasca process have been reported to equal up to ninety percent (90%) of the available bitumen content. This process also has been reported to have limited commercial viability as it has been unsuccessfully applied to other tar sand deposits.
Other processes known to have been applied to tar sands include the usage of organic solvents for dissolution of bitumen in like chemistries. Variations on the basic use of organic solvents range from the usage of bilayers, a hydrocarbon based solvent layer and a distinct aqueous layer, the use of diluents as preconditioners, and straight forward solvent extractions. In each of the above applications, the solvent is a factor in mobilizing or segregating the bitumen product for the purposes of collection. In some cases additional chemistries come into play such as the use of caustics, wetting agents or surfactants, some of which help to promote more complete mechanical separation of the oils from the sand matrix.
Other methods for extracting oil from tar sands have been demonstrated, however many of these relate to tar sands originating from a particular source, thus possessing characteristics that may allow a chemical advantage in separation. A broad based extraction process for tar sands, utilizing low cost, aqueous formulated chemistries that are functional at moderate to low temperature conditions has not been developed.
The present invention surprisingly achieves the goals of economy and effectiveness with such aqueous based chemistries. The separation chemistry of the present invention employs in part a composition disclosed in U.S. Pat. No. 4,514,325, issued to Russo et al., the subject of that reference being a unique coupling agent generally described as a sulfonated fatty acid alkali metal salt. The compatibility of the present invention with varying conditions and kinds of oils or bitumens allows it to be utilized in related extraction applications, such as the recovery of oils spilled onto the ground. These and other advantages and distinctions of the present invention will become apparent as discussed within.